Effects of Supplemental O2 Inhalation on Cerebral Oxygenation During Exercise in Patients With Left Ventricular Dysfunction

Abstract

It has been recently reported that cerebral oxyhemoglobin (O(2)Hb) decreases during exercise in nearly 50% of patients with dilated cardiomyopathy. The present study evaluated whether the inhalation of supplemental O(2) diminishes the decrease in cerebral O(2)Hb during exercise. Ten patients with a left ventricular ejection fraction <50% and a clearly observable decrease in cerebral O(2)Hb during preliminary exercise testing underwent 2 additional symptom-limited incremental exercise tests: 1 while breathing room air (control) and the other while breathing 50% O(2). In the latter test, the switch from room air to 50% O(2) was performed, on average, at 43.0+/-14.2 W. Cerebral O(2)Hb was continuously monitored during exercise using near-infrared spectroscopy. In the control exercise test, cerebral O(2)Hb gradually decreased as the work rate increased in all the subjects. When the subjects breathed 50% O(2), this decrease in cerebral O(2)Hb was diminished. The change in cerebral O(2)Hb from rest to peak exercise during the test under 50% O(2) was significantly higher than that during the control test (-0.23 +/-1.89 vs -2.47+/-1.57 micromol/L, p=0.002). Similarly, the change in the cerebral tissue oxygenation index was significantly higher in the test under 50% O(2) (0.45 +/-4.46 vs -3.33+/-3.06%, p=0.023). Impaired cerebral oxygenation during moderate to heavy intensity exercise in patients with left ventricular dysfunction can be offset by breathing supplemental O(2).